fix arity difference between Procs and lambdas (see #293 for details)

CHANGELOG.md

@@ -1,5 +1,9 @@
 # CHANGELOG
 
+## unreleased
+
+ * fix arity difference between Procs and lambdas (see [issue #293](https://github.com/aasm/aasm/issues/293) for details)
+
 ## 4.5.1
 
  * make sure to use override configuration options if state machine is defined more than once (see [issue #287](https://github.com/aasm/aasm/issues/287) for details)

lib/aasm/core/transition.rb

@@ -55,7 +55,7 @@ module AASM::Core
         arity = record.send(:method, code.to_sym).arity
         arity == 0 ? record.send(code) : record.send(code, *args)
       when Proc
-        code.arity == 0 ? record.instance_exec(&code) : record.instance_exec(*args, &code)
+        code.parameters.size == 0 ? record.instance_exec(&code) : record.instance_exec(*args, &code)
       when Array
         if options[:guard]
           # invoke guard callbacks

spec/models/guardian.rb

@@ -1,6 +1,9 @@
 class Guardian
   include AASM
 
+  def inner_guard(options={})
+  end
+
   aasm do
     state :alpha, :initial => true
     state :beta
@@ -12,6 +15,13 @@ class Guardian
       transitions :from => :alpha, :to => :beta, :guard => :fail
     end
 
+    event :use_proc_guard_with_params do
+      transitions :from => :alpha, :to => :beta, :guard => Proc.new { |options={}| inner_guard(options) }
+    end
+    event :use_lambda_guard_with_params do
+      transitions :from => :alpha, :to => :beta, :guard => lambda { |options={}| inner_guard(options) }
+    end
+
     event :use_guards_that_succeed do
       transitions :from => :alpha, :to => :beta, :guards => [:succeed, :another_succeed]
     end

spec/unit/guard_spec.rb

@@ -27,6 +27,18 @@ describe "per-transition guards" do
     expect { guardian.use_guards_where_the_second_fails! }.to raise_error(AASM::InvalidTransition)
     expect(guardian).to be_alpha
   end
+
+  describe "with params" do
+    it "using a Proc" do
+      expect(guardian).to receive(:inner_guard).with({:flag => true}).and_return(true)
+      guardian.use_proc_guard_with_params(:flag => true)
+    end
+
+    it "using a lambda" do
+      expect(guardian).to receive(:inner_guard).with({:flag => true}).and_return(true)
+      guardian.use_lambda_guard_with_params(:flag => true)
+    end
+  end
 end
 
 describe "event guards" do